What is Gynecomastia Gynecomastia, also known as excessive male breast development, is usually associated with an increase in breast glandular tissue and a lack of male sex hormones, and is more likely to be found in infants, young adults, and older men. The root cause of male breast enlargement or enlargement is usually male breast development. Breast development usually occurs during female puberty, but males also have breast development, a condition that can lead to breast enlargement in men, but this condition can also be caused by a number of diseases, and in order to prevent the condition from affecting patients, they need to receive treatment as soon as possible.